The present invention relates to beverage dispensers and in particular electronically controlled beverage dispensers of the ice bank type.
Beverage dispensers are well known in the art and are typically used to dispense carbonated beverages consisting of a combination of syrup and carbonated water. Beverage dispensers of the ice bank variety use refrigeration equipment including a compressor, condenser and evaporator to form an ice bank around the evaporator coils. The ice bank is suspended in a tank of cold water and provides a cooling reserve for the carbonated water and syrup beverage constituents.
A major problem with the ice banks concerns the regulation of the size thereof. Mechanical and electro-mechanical controls are known, however such controls can be slow to respond and therefore result in wider than desired fluctuation in the size of the ice bank. Electronic controls are known whereby a pair of probes determine the presence of ice or water as a function of the conductivity thereof. However, early electronic controls suffered from reliability problems, and the probes over time can become corroded and therefore provide unreliable information. Furthermore, both mechanical and electronic controls have the problem of hysteresis management wherein undesirable short cycling of the refrigeration compressor can occur. Such prior art controls have not been able to determine with a high degree of certainty if ice is present, and if so is there is sufficient thickness that further ice production should be terminated.
A similar problem exists in current art beverage dispensers with respect to the carbonator. The carbonator, of course, is the vessel wherein plain water and carbon dioxide are combined to produce the carbonated water. Typically, a carbonator includes a probe positioned therein having high and low probe contact points for electronically determining the level of water within the carbonator. Specifically, the probes determine the presence of water or air with respect to the difference in electrical resistance there between. Prior art level controls of this type, as with ice bank controls, suffer with the problem of accuracy. The interior of the carbonator is a dynamic environment where water and carbon dioxide are being combined causing turbulation and spray. Thus, it has always been difficult to know if the water is in fact sufficiently low to require water to be pumped to the carbonator. Since it is difficult to know the level of the water in the tank, it is also difficult to build in any form of hysteresis control so that the pump is not short cycled.
A further problem with prior art dispensers of the ice bank type concerns the control of the agitator motor. The agitator motor is used to circulate water within the water tank in which the ice bank resides to enhance heat exchange between the ice and the water and ultimately the beverage constituents. In such prior art dispensers agitator motors are generally operated continuously. However, such use of electrical power is wasteful, especially during periods of time wherein the dispenser is not in use. Thus, it would be desirable to operate the agitator motor more in accordance with the actual need thereof.
It is also known that the carbonator can become less effective at carbonating plain water over time. This can occur as a result of oxygen and other gases entrained in the water being released therefrom within in the carbonator. Eventually, the air space within the carbonator that is ideally totally carbon dioxide, can include a substantial percentage of oxygen, nitrogen, and so forth. Thus, various strategies have been proposed to use a solenoid operated valve to periodically vent air from the carbonator air space and replace it with carbon dioxide. However, such devices typically purge air from the carbonator based upon a predetermined time lapse. It would be more desirable to purge the carbonator based more directly upon the actual presence of contaminating gases as opposed to the lapse of a predetermined period of time where such purging may occur needlessly.
The present invention is an electronic control for use with a beverage dispenser, and particular a beverage dispenser of the ice bank type. Such a beverage dispenser includes a water tank for holding a volume of water. The water is refrigerated by an evaporator suspended therein and connected to a compressor and a condenser. A fan motor is used to cool the condenser. A plurality of syrup lines extend through the tank for cooling thereof and are connected to a plurality of beverage dispensing valves secured to the beverage dispenser. In the preferred embodiment, a carbonator is positioned within the water tank to provide for direct cooling thereof. The carbonator includes a level sensor having low and high sensing contact points and includes a solenoid operated safety valve. The carbonator has a plurality of carbonated water lines extending therefrom for connection to the plurality of beverage dispensing valves. An agitator motor is secured to the dispenser and includes a shaft and an agitating plate for providing movement of the water in the water bath. An ice bank sensor is positioned within the water bath with respect to the evaporator coils to provide for the formation of the desired sized ice bank on the evaporator coils. The ice bank sensor includes two probes across which an electrical pulse can be generated. A temperature sensing probe is positioned with respect to the evaporator coils so that it exists centrally within the ice bank. A water pump provides for pressurized delivery of plain water to the carbonator tank.
The electronic control of the present invention includes a microprocessor connected to and receiving information from the ice bank sensor, the temperature sensor and the carbonator level sensor. In turn, the microprocessor is connected to and provides for the control, of the solenoid safety valve, the agitator motor, the water pump and the compressor. Of course, the ice bank sensor, the temperature sensor, the carbonator level sensor, the solenoid safety valve, the agitator motor, the water pump and the compressor all have specific circuitry associated therewith through which the microprocessor exercises control and receives information. Power is supplied to the microprocessor by a regulated supply and further input is provided thereto by a zero crossing circuit. A constant reference voltage circuit is supplied to the microprocessor and to the ice bank probe and carbonator probe.
The microprocessor is programmed to control the ice bank sensor and related circuitry wherein a DC signal is alternately permitted to flow in opposite directions between the two probes thereof.
The microprocessor is programmed to control the ice bank sensor and related circuitry wherein the presence or not of ice is determined by the change in resistance to electrical flow between the probes thereof. However, unlike the prior art a DC signal is alternately permitted to flow in opposite directions between the two probes thereof. Moreover, this energizing of the probes only occurs when readings are to be taken, otherwise there is no potential there between. Furthermore, it was found that if each sampling occurs for a period of time of less than 4 milliseconds, corrosive deposition from one probe to the other can be avoided. Also, the alternating of the direction of the current flow further serves to negate any deposition that could occur over time as well as permit the use of DC current which allows for simpler and less costly circuitry than with the use of AC current as seen in the prior art. The sampling is controlled by software wherein 8 readings are taken after which the two highest and two lowest readings are thrown out and the remaining four are averaged. The resulting reading is compared to high and low set points that have been experimentally determined based upon the known range of water qualities as well as the particular dimensions of the ice sensor, its specific performance in water of varying ionic and particulate content and so forth. Thus, the compressor will be signaled to turn on to build the ice bank if the sensed resistance is below the low set point, and conversely will be turned off if the averaged reading is above the high set point. No change in the current state, whether it be make ice or not make ice, will occur if the averaged reading is between the low and high set points. The high and low set points therefore provide for hysteresis management so that the determination of the existence of ice or not over the probes can be done with a high degree of reliability. In addition, a reading of the temperature probe is also taken simultaneously with the determination of the resistance between the ice bank probes. If the determination is that ice is present over the probes, an increment, in the present case 0.9 degrees F. as experimentally determined, is subtracted from the current ice bank temperature reading. Rather than immediately turning off the compressor, it is left running until the ice bank temperature probe reads this lower temperature. As is understood by those of skill, to increase the size of an ice bank requires the refrigeration system to work progressively harder. Thus, there is a correlation between the temperature within the ice bank and its overall size or thickness. Therefore, by permitting the compressor to run based upon the temperature of the ice bank, a further desired amount of ice can be safely and accurately added to the ice bank beyond the physical position of the probes. In addition, ambient load proportionally affects the amount of ice which is added to the ice bank. The product of the refrigeration system cooling rate and the ice thickness forms the basis for determining the amount of ice added. As the ambient load increases, the refrigeration cooling rate decreases, forming increased or additional ice reserve compared to nominal ambient loads. The increased ice reserve is beneficial to provide additional cooling reserve when needed in higher ambients. The reverse also hold true wherein lower than nominal ambients will produce less ice when additional cooling is not needed. It can be seen that such an approach further protects against undesirable short cycling of the compressor as is not turned off at the first indication of ice at the ice sensing probes, which particularly during a period of high volume beverage dispensing, could very quickly result in melting of that ice and a determination that ice should again be produced.
The carbonator probes also use a DC signal, but, unlike the ice bank sensor probes. since the current flow is not between the high and low water level probes but between each probe and the grounded carbonator tank, reversal of such flow is not necessary. However, in the carbonator level sensing circuit, like that of the ice bank sensing circuit, current is not present at the high and low probes unless readings are being taken. The microcontroller software then directs the sampling of each probe 64 times in time spans of less than 4 milliseconds to prevent any corrosive degradation. The 64 samples provide for determining with high reliability that each probe is either in air or water. If they are both in air the water pump is turned on, if they are both in water the pump is turned off. If the high and low water level probes disagree, that is, one is in air and the other in water, then no change is made to the current pump operation.
The carbonator safety valve is operated periodically based upon an accumulation of pump run time. Thus, unwanted gases are released from the carbonator based upon a factor that relates directly to the presence of those unwanted gases therein.
The agitator motor is operated as a function of the temperature sensed by the temperature probe during initial start up of the dispenser when no ice is present on the evaporator coils. Also, the agitator is operated on the basis of whether or not the compressor and/or the carbonator pump have been running during a predetermined time period. Thus, if no drinks have been drawn during the predetermined time period, as indicated by no running of the water pump, or the compressor has not been running during that time period, also indicating no drink dispensing requiring ice bank replenishment, the agitator is turned off. Such agitator control was found to decrease the amount of time needed for and initial pull down forming a full ice bank, and to save energy by not running the agitator motor and not running the compressor to replace ice needlessly eroded by constant running of the agitator.